Advertisements can be included in various forms of offline media. For example, offline ads, such as broadcast on radio, can be a powerful way for advertisers to reach an audience. Members of the audience can be influenced, e.g., to make purchases, investigate products or use services that are advertised. Offline media providers, such as radio stations and newspapers, can make advertising inventory available to advertisers. Advertising inventory can include advertising spots (e.g., 30-second time slots in a radio broadcast or parts of a newspaper page) and can be allocated to advertising campaigns. Allocating can include scheduling and reserving the spot for a particular campaign. An advertising campaign can be a comprehensive advertising plan that consists of a series of messages published or broadcast in a variety of media over a specific time frame. Advertisers can create campaigns that center on a single theme or idea, such as to promote a product or service. The campaign messages, sometimes called “creatives,” can be media content such as recorded audio or video. The campaign messages can be referred to generically as advertisement messages or simply as advertisements.